Jon Lomberg’s Portrait of the Milky Way: Finder chart

Exploring our surroundings without taking a single step is challenging. On Earth, we are essentially rooted to a single spot, looking out at the larger galaxy around us: the Milky Way. Astronomers have been mapping the Milky Way for centuries. Over time, our picture of its shape and structure has grown increasingly clearer as our ability to see distant objects and measure their distances improves.

This unique poster shows our current understanding of the Milky Way Galaxy in which we live. It represents the culmination of both scientific and artistic efforts to visualize our local neighborhood within the cosmos, and reflects our most detailed and accurate data to date.

You are here
Artist Jon Lomberg says, “When you see a group photograph, you look for yourself first.” In his painted Portrait of the Milky Way, the Sun (1) stands out near the center of the image. But our star and the solar system in which we live are actually located about 25,000 light-years from the bright center of our galaxy, called the bulge.

Astronomers currently believe the Milky Way Galaxy contains upwards of 400 billion stars. From above, it is disk-shaped and roughly 100,000 light-years from end to end, with an edge-on “width” of several thousand light-years. In the center lies a slightly elongated, or bar-shaped, bulge (20, 21). Extending from the bulge of the galaxy are its spiral arms, areas where gas, dust, and stars “pile up” as they orbit the center of the galaxy; it takes the Sun just over 200 million years to make a complete rotation.

The Sun is located in the Orion Arm (A), once pictured as a small branch or spur off the larger Sagittarius-Carina Arm (C). However, recent research indicates that our Orion Arm may be more like the galaxy’s other major arms —Perseus (B), Norma (D), and Scutum (E) — than previously thought.

Surrounding the entire galaxy like a dim, spherical cloud is our Galactic Halo (26). The halo contains our galaxy’s oldest stars, largely within its roughly 150 known globular clusters — including the rich Omega Centauri Globular Cluster (25), readily visible from Earth’s Southern Hemisphere. Although invisible on this map, our galaxy is also surrounded by a massive halo of dark matter as well. Our dark matter halo only interacts with the normal matter in our galaxy via its gravitational influence; it has left its fingerprint in the structure and behavior of the visible matter we do see.

Our Milky Way Galaxy is part of a Local Group of at least 54 known galaxies bound together by gravity. The Milky Way is the second-largest galaxy in this group. The Andromeda Galaxy, M31 (27), is the largest member, about twice the size of our home and roughly 2.5 million light-years away. The Triangulum Galaxy, M33 (28), about 3 million light-years distant, is the third-largest member of our Local Group. Astronomers believe it is bound to Andromeda as a satellite galaxy, orbiting and fated to possibly merge with it to become part of a larger structure.

Andromeda Galaxy

Kees Scherer

The Milky Way has several satellite galaxies as well. It is in the process of cannibalizing, or destroying, many of these, including the Sagittarius Dwarf Galaxy (22). From our viewpoint on Earth, a “stream” of stars arcs from the dwarf’s location on the far side of the Milky Way (23), trailing across the sky (24) as the material encircles, joins, and ultimately grows our galaxy.

Looking out
When we map our Milky Way, we are limited by our viewpoint. We can only view the galaxy from Earth — or very near Earth — and have thus mapped the region closest to our place on the Orion Arm much more easily than the rest of the galaxy. Because brightness diminishes quickly with distance, and even faster with the obscuration of the dust found throughout our galaxy, you’ll see that the majority of our labeled objects fall relatively close to the Sun.

There are ways, however, to look beyond our closest spiral arms. One of the best examples of a serendipitous workaround, provided by the galaxy’s structure itself, is Baade’s window (19), named for astronomer Walter Baade. This is an area of the Milky Way low in dust content. When we look in this direction from Earth, we see the bright disk of the Milky Way without heavy obscuration, allowing astronomers to study the more distant bulge and its components in better detail. If you were to look up at the sky, Baade’s window is located near the constellation Sagittarius, which is also the direction of the galactic bulge.

Pillars of Creation (Eagle Nebula)

NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Local Character
The Kepler spacecraft searched for extrasolar planets (18) among the stars in a narrow region along the Orion Arm, looking “ahead” of us in the direction of the galaxy’s rotation (the spiral arms of a galaxy generally trail its direction of rotation). This dataset itself only represents the smallest fraction of extrasolar planets likely found throughout our galaxy, as planetary systems now seem the norm, rather than the exception, around most stars.

Our map also highlights some of the most recognizable objects in the night sky; you can see that most are contained within the Orion Arm, and all are on the “near” side of the bulge in the closest spiral arms. These local objects range from young clouds of gas and dust just beginning to form stars to the last remaining wispy, tangled vestiges of long-dead massive stars.

Within the Sagittarius-Carina Arm are the Eagle (2), Omega (3), Trifid (4), and Lagoon (5) nebulae. These objects host stellar nurseries composed of massive clouds of dust and hydrogen gas, dotted throughout with forming stars loosely bound in open clusters. The Eagle Nebula is particularly famous as the home of the Pillars of Creation, one of the most iconic images ever captured by the Hubble Space Telescope. The Trifid Nebula is named for its unique morphology — the distinct veins of a dark nebula appear to divide it in three.

Eta Carinae Nebula

ESO/IDA/Danish 1.5 m/R.Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron

On the other end of the age spectrum, the Gum Nebula (16) is a faint, expanding supernova remnant about one million years old. It also contains the smaller, roughly 12,000-year-old Vela supernova remnant, which left behind the Vela pulsar. The Eta Carinae Nebula (17) is a large emission nebula that houses not only young star clusters, but also several supernova remnants and one or more massive, bright stars in its center that are expected to explode as supernovae in the future.

Crab Nebula

NASA, ESA, J. Hester and A. Loll (Arizona State University)

Thanks to their proximity, the objects in our own Orion Arm appear as some of the brightest and most striking. They include the Cocoon (6), North America (7), California (9), Flaming Star (10), Cone (12), and Rosette (15) nebulae, which are formed by swaths of ionized gas lit by nearby bright stars. Many of these also contain bright, young open clusters of stars and localized regions of new star formation. The iconic and easily visible Orion Nebula (11) is one of the closest star-forming regions to Earth, allowing astronomers an up-close view of this important process.

The Cygnus Loop or Veil Nebula (8) and Crab Nebula (14) are nearby supernova remnants; though the creation of the Cygnus Loop predates recorded human history, it would have been visible from Earth. The Crab Nebula contains a pulsar and is associated with a supernova seen in the year 1054.

Looking outward from the center of the galaxy, the Cassiopeia OB6 (13) association is a group of huge, hot young stars with massive stellar winds located in the Perseus Arm.

Orion Nebula

ESO/H. Drass et al.

Our portrait of the Milky Way
This exquisite map of our Milky Way Galaxy has been hundreds of years in the making. It reflects the most up-to-date research available, including the ever-increasing number of known exoplanets and recent findings indicating that the Orion Arm is longer and more clearly separated from the Sagittarius Arm than previously believed.

Today, astronomers continue to develop the picture of our home galaxy from within, largely using infrared and radio emissions to penetrate the dust that obscures our view in optical wavelengths. Researchers are also studying other galaxies considered Milky Way analogues to better understand the processes that have built and continue to shape our galaxy. Filling in the puzzle pieces of our own home will in turn teach us about galactic structure and evolution as we seek to understand how galaxies throughout the universe form, grow, and change.

You can see more of the objects highlighted in this poster in our online gallery.